Extracting bitumen from mined oil sands offers the possibility of addressing future needs for energy. Present-day methods for separating the bitumen from the inorganic species in oil sands are inefficient and costly, however. A major inefficiency arises from the need to use heat for bitumen extraction. Providing the needed heat is itself expensive and requires energy. Furthermore, heat provided in the form of hot water for extraction is lost to the environment as hot water run-off after its exposure to the oil sands. The hot water run-off contains non-recyclable heat energy that adds additional stresses to the environment.
Presently, the bituminous ore mined from the oil sands ore is crushed and mixed with water heated to 55° C. to “condition” the ore for separation. This temperature is far in excess of the ambient temperature in the environment. The mixture thus prepared, also called a “slurry,” may be alkalinized by the addition of a strong caustic agent, typically sodium hydroxide. The slurry is then pumped through a hydrotransport pipeline, where mechanical turbulence further assists with separating bitumen from the inorganic sands. The two to three kilometer long hydrotransport pipelines conduct the slurry to processing facilities. When received in a processing facility, the separated slurry is aerated and sent to a gravity separation vessel. Spent sands are ejected from the bottom of the gravity separator. Meanwhile, the aerated bitumen floats to the top and is removed for further froth treatment and upgrading to synthetic crude oil.
There has been a decrease in the temperature requirements over the years from the original Clark hot water process that required a water temperature of 85° C. to the present-day processes that use water temperatures of approximately 55° C. Nonetheless, a considerable amount of energy is required to heat the water used in processing the mined oil sands and extracting the bitumen there from. In the procedure described above, the oil sands slurry being processed contains about 20-30% oil sands by weight, with the rest of the processed volume (about 70-80%) being water. A significant amount of energy is required to maintain the slurry water temperature at this level.
Hot water extraction is particularly difficult in a northern latitude location like the Athabasca oil sand field. The climate in northern Alberta ensures that oil sands mining and subsequent bitumen extraction must be carried out in cold temperatures for much of the year. Edmonton, Alberta, for example, has a mean January temperature of −11.7° C., and an average of 178.6 days per year with a temperature less than 0° C. The average annual snowfall is 123.5 cm. In January, 1911, a record low temperature of −61.1° C. was reported. The mean July temperature is 17.5° C. (Preceding data obtained from The Canadian Encyclopedia, online edition at http://www.thecanadianencyclopedia.com/index.cfm?PgNm=TCE&Params=A1SEC89 2428). This environment makes heat processing of oil sands for bitumen extraction more difficult and less efficient, especially in view of the long exposure of the slurry to cold temperatures while in transit within the hydrotransport pipelines.
Oil sands processing facilities have recognized that a lower-temperature separation technology could lower the cost of bitumen extraction. A number of technologies have offered methods for lowering the required extraction method, for example, U.S. Pat. Nos. 4,425,227 and 4,946,597. There remains a need in the art, however, for lower-temperature extraction methods, including those that can be conducted at ambient or subambient temperatures.